//<p>给定一个 N 叉树，返回其节点值的<em>层序遍历</em>。（即从左到右，逐层遍历）。</p>
//
//<p>树的序列化输入是用层序遍历，每组子节点都由 null 值分隔（参见示例）。</p>
//
//<p> </p>
//
//<p><strong>示例 1：</strong></p>
//
//<p><img src="https://assets.leetcode.com/uploads/2018/10/12/narytreeexample.png" style="width: 100%; max-width: 300px;" /></p>
//
//<pre>
//<strong>输入：</strong>root = [1,null,3,2,4,null,5,6]
//<strong>输出：</strong>[[1],[3,2,4],[5,6]]
//</pre>
//
//<p><strong>示例 2：</strong></p>
//
//<p><img alt="" src="https://assets.leetcode.com/uploads/2019/11/08/sample_4_964.png" style="width: 296px; height: 241px;" /></p>
//
//<pre>
//<strong>输入：</strong>root = [1,null,2,3,4,5,null,null,6,7,null,8,null,9,10,null,null,11,null,12,null,13,null,null,14]
//<strong>输出：</strong>[[1],[2,3,4,5],[6,7,8,9,10],[11,12,13],[14]]
//</pre>
//
//<p> </p>
//
//<p><strong>提示：</strong></p>
//
//<ul>
//	<li>树的高度不会超过 <code>1000</code></li>
//	<li>树的节点总数在 <code>[0, 10^4]</code> 之间</li>
//</ul>
//<div><div>Related Topics</div><div><li>树</li><li>广度优先搜索</li></div></div><br><div><li>👍 194</li><li>👎 0</li></div>
  
package leetcode.editor.cn;

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;

public class _429_NAryTreeLevelOrderTraversal{
    public static void main(String[] args) {
         Solution solution = new _429_NAryTreeLevelOrderTraversal().new Solution();
    }
    //leetcode submit region begin(Prohibit modification and deletion)
/*
// Definition for a Node.
class Node {
    public int val;
    public List<Node> children;

    public Node() {}

    public Node(int _val) {
        val = _val;
    }

    public Node(int _val, List<Node> _children) {
        val = _val;
        children = _children;
    }
};
*/

class Solution {
    public List<List<Integer>> levelOrder(Node root) {
        List<List<Integer>> result = new ArrayList<>();
        if (root==null) {
            return result;
        }
        LinkedList<Node> queue = new LinkedList<>();
        queue.offer(root);
        while (!queue.isEmpty()) {
            int size = queue.size();
            List<Integer> l = new ArrayList<>();
            for (int i = 0; i < size; i++) {
                Node poll = queue.poll();
                l.add(poll.val);
                List<Node> children = poll.children;
                if (children!=null && !children.isEmpty()) {
                    for (Node child : children) {
                        queue.offer(child);
                    }
                }
            }
            result.add(l);
        }
        return result;
    }
}
//leetcode submit region end(Prohibit modification and deletion)

}